1、Standard Method of Test for Quantitative Determination of the Percentage of Lime in Asphalt Mixtures AASHTO Designation: T 362-171Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August 2017) American Association of State Highway and Transportation Officials 444 North Capitol Stree
2、t N.W., Suite 249 Washington, D.C. 20001 TS-2c T 362-1 AASHTO Standard Method of Test for Quantitative Determination of the Percentage of Lime in Asphalt Mixtures AASHTO Designation: T 362-171Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August 2017) 1. SCOPE 1.1. This method co
3、vers the quantitative determination of the percentage of lime in asphalt mixtures by calculation of the calcium hydroxide, Ca(OH)2, recovered from a sample of the mixture. A specimen is obtained through drilling into the asphalt mixture and collecting the drilling dust. The specimen is subjected to
4、an acid filter boil and wash and is analyzed using either Atomic Absorption (AA) Spectrometry or Ion Exchange Chromatography (IEC). 1.2. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated
5、with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materials R 6
6、7, Sampling Asphalt Mixtures after Compaction (Obtaining Cores) T 308, Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method 2.2. ASTM Standard: C25, Standard Test Methods for Chemical Analysis of Limestone, Quicklime, and Hydrated Lime 3. SIGNIFICANCE AND USE 3.1. T
7、his test method is useful for determining the amount of lime added to an asphalt mixture. 3.2. If the coarse aggregate contains limestone, the limestone aggregate will be dissolved by the acid used in this method and can yield an unrealistically high result. If limestone is present in a relatively m
8、inor amount, it is possible to run a background analysis on the raw aggregate. An adjustment can then be made based on the background analysis in order to better approximate the actual results. If the aggregate in the asphalt mixture contains an appreciable amount of limestone, this test method is n
9、ot suitable. Depending on the concentration, the calcium content of any added lime could be masked by the aggregate concentration. This effect would lead to a significant error in overestimation of the amount of lime added. 2017 by the American Association of State Highway and Transportation Officia
10、ls. All rights reserved. Duplication is a violation of applicable law.TS-2c T 362-2 AASHTO 4. APPARATUS 4.1. Atomic Absorption (AA) Spectrometry or Ion Exchange Chromatography (IEC)These devices measure the concentration of chemical elements, in this case calcium, in aqueous solutions. AA Spectromet
11、ry measures the intensity of a characteristic color imparted to a flame by the presence of calcium ions in the test solution. IEC measures the change in electrical conductivity of the solution. IEC can identify components of mixtures; AA Spectrometry can only measure one element at a time. 4.2. Bala
12、nceAn analytical balance conforming to M 231, Class B. 4.3. Heating DeviceA small hot plate or other suitable device shall be available for supplying sufficient heat under the flask to bring the solution to a boil. Suitable shields, baffle plates, or sand baths shall be used on the surfaces of the h
13、ot plates to minimize localized overheating. 4.4. Rotary HammerAn industrial size hammer drill with a 3/8-in. carbide drill bit. 4.5. Miscellaneous Equipment: 4.5.1. Automatic PipetteEppendorf or equivalent of adequate capacity to obtain a 1.0-mL sample. 4.5.2. Filter FunnelBuchner or equivalent and
14、 filter paper, filter flask, and a vacuum source. 4.5.3. Glassware100- and 250-mL flasks. 5. TEST SPECIMENS 5.1. Test specimens may be either laboratory-mixed asphalt mixtures or sampled from asphalt pavements according to R 67. 5.2. Pavement specimens shall be taken from pavements with a core drill
15、, diamond or carborundum saw, or by other suitable means. Specimens will be further prepared as noted in Section 6.1. 5.3. Specimens shall be free from foreign materials such as foundation material, soil, paper, foil, etc. 5.4. If the core contains more than one pavement layer, it is recommended tha
16、t the layers be separated by sawing or other suitable means. 6. PROCEDURE 6.1. Determine the percentage of binder in the mix by testing the specimen from Section 5 according to T 308. 6.2. Determine the percentage of calcium hydroxide in the lime according to ASTM C25. Report the value in decimal fo
17、rm to the nearest 0.001. 6.3. Preparation of Specimen: 6.3.1. A specimen is obtained from the drilling dust of a pavement core or laboratory-mixed asphalt mixture sample. Stand the core on a thick piece of wood and use a heavy-duty rotary hammer with a 3/8-in. carbide bit to drill into the sample. 2
18、017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 362-3 AASHTO Note 1A rotary hammer that utilizes SDS, SDS Max, or spline shank bits is recommended. Devices utilizing straight shank bits have been
19、 found to be insufficient. Depending on the number of samples, it may be worthwhile to make a frame to hold the core. Note 2It is recommended to wear safety glasses and protective gloves. 6.3.2. Drill to the depth of the drill flutes. This depth will yield about 15 g of dust. Discard any lumps of th
20、e core that may break off. 6.3.3. Take the 15 0.5 g of dust and determine its mass to the nearest 0.01 g. Place the dust in a 250-mL conical flask. Add 100 mL of 4 percent acetic acid and boil the mixture for 30 to 45 min. Filter the mixture through a filter funnel (Buchner or equivalent) and wash t
21、he insoluble dust with distilled water. 6.3.4. Transfer the filtrate to a 250-mL volumetric flask. Rinse the filter flask with distilled water and add the washings to the contents of the volumetric flask. Add distilled water to the flask until the total volume of its contents reaches 250 mL. Place a
22、 stopper in the flask, and shake it well to mix the contents. 6.3.5. Use a pipette (an Eppendorf automatic pipette or equivalent) accurate to 0.1 mL to take a 1.0-mL aliquot from the volumetric flask, and transfer this specimen to a 100-mL volumetric flask. Fill the flask with distilled water until
23、the total volume of its contents reaches 100 mL. Place a stopper in the flask, and shake it well to mix the contents. 6.4. Analyze the drilling dust to determine the level of calcium ions present: 6.4.1. Run AA Spectrometry or IEC (according to the manufacturers recommendations) on the specimen prep
24、ared in Section 6.3.5. Run calcium standards before and after the specimen analysis. If using AA Spectrometry, do not add lanthanum salts. Note 3Theories exist that calcium is subject to interference with AA Spectrometry and this condition can be overcome by adding lanthanum salts. However, in this
25、procedure, it has been found to provide an artificially high lime result. 6.4.2. The calcium ion concentration in the specimen should be in the range of 1 to 5 mg/L. If the concentration is outside this range, it indicates the possible presence of limestone aggregate (see Section 3.2). 7. CALCULATIO
26、N OF RESULTS 7.1. Calculate the percentage of lime in the asphalt mixture as follows: ( ) ( ) 46.25 / 10 100 /100dcC W ACLL = (1) where: L = percentage of lime; C = concentration of calcium from AA or IEC, mg/L; Wd= mass of the dust, g; AC = percentage of the binder in the mix, determined by T 308;
27、and Lc= percentage of calcium hydroxide in the lime from ASTM C25 in decimal form to the nearest 0.001 (e.g., 0.955). 7.1.1. Derivation of Equation 1: The calcium content of the original solution is: 2017 by the American Association of State Highway and Transportation Officials. All rights reserved.
28、 Duplication is a violation of applicable law.TS-2c T 362-4 AASHTO C 100/4 mg/L or C 25. Hydrated lime is calcium hydroxide Ca(OH)2with a molecular weight of 40 + 2(16 + 1) = 74. To convert from mg/L of calcium to mg/L of lime, multiply by 74/40 or 1.85. Therefore, the hydrated lime content is: C 25
29、 1.85 mg/L or C 46.25 mg/L Hydrated lime is added to the mix as a percentage of the aggregate; therefore, the mass of the aggregate in the dust specimen is included as 1000 Wd (100 AC)/100 in grams or 10 Wd (100 AC)/100 in milligrams. 8. REPORT 8.1. The report shall include the following information
30、: 8.1.1. Type of specimen tested (obtained from a laboratory-mixed sample or pavement core sample); Note 4For core specimens, the height of each test specimen in millimeters (or inches) should be reported. 8.1.2. Date of the test; 8.1.3. Asphalt mixture identification; 8.1.4. Percentage of asphalt b
31、inder to the nearest 0.1 percent; and 8.1.5. Percentage of lime to the nearest 0.01 percent. 9. PRECISION AND BIAS 9.1. No precision and bias statements are available at this time. 10. KEYWORDS 10.1. Asphalt mixture; Atomic Absorption Spectrometry; Ion Exchange Chromatography; lime. 1Formerly AASHTO Provisional Standard TP 72. First published as a full standard in 2016. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.
